Mechanism for clamping flexible printing plates to the plate cylinder of machines for flat printing



3 G N T. M W R P F u E L T N NB Im NX HR C P Dec. 5, 1961 K. P. HARTMA MECHANISM FOR 'CLAMPING FLE PLATES TO THE PLATE MACHINES FOR FLAT 4 Sheets-Sheet 1 Filed Feb. 9, 1959 INVENTOR. K P/JT/A/V Firm Ahrrmm fl/w x/w Arry.

Dec. 5, 1961 K. P. HARTMANN 3,01

MECHANISM FOR CLAMPING FLEXIBLE PRINTING PLATES TO THE PLATE CYLINDER OF MACHINES FOR FLAT PRINTING a y/wzw 1961 K. P. HARTMANN 3,011,437

MECHANISM FOR CLAMPING FLEXIBLE PRINTING PLATES To THE PLATE CYLINDER OF MACHINES FOR FLAT PRINTING Filed Feb. 9, 1959 4 Sheets-Sheet 3 5 .52 5 /8 a 44' /4 I 5a 82 as 3 I 2O 2 E-NNNN uuumuuu Jo INVENTOR. {Warm/v 6 75)? fiwr/wl/wv Dec. 5, 1961 Filed. Feb. 9,

K P. HARTMANN MECHANISM FOR CLAMPING FLEXIBLE PRINTING PLATES TO THE PLATE CYLINDER OF MACHINES FOR FLAT PRINTING 4 Sheets-Sheet 4 1' 1 36 32 .28 3 F9 /2 w I #248 as IN VENTOR.

Filed Feb. Claims priority, application Denmark Jan. 31, 1959 14 Claims. (Cl. fill-415.1)

This invention relates to a mechanism for clam-ping a flexible printing plate to the plate cylinder of machines, particularly high speed rotary machines, for fiat printing, especially for oft-set printing, wherein the ends of a printing plate are connected to two bars,- which are received in an axially extending groove in the circumferential surface of the cylinder.

Such mechanisms have until now been made in many different ways. It has e.g. been suggested to arrange a number of pins transversely of the bars, the said pins when turned in one direction or the other cooperating with the bars and the walls of the groove for adjustment and tightening of the printing plate. Some of the pins cooperate by means of screw threads with one of the bars, some others with the other bar, and still others cooperate by means of eccentrics with both bars and substantially serve to tighten the printing plate around the plate cylinder. Such a mechanism has proved expedient in practice, but makes heavy demands on care and precision in order to achieve correct tightening and even tension of the printing plate.

One object of the present invention is to provide a mechanism for clamping a flexible printing plate to the plate cylinder of a printing machine of the kind in question, in which the above mentioned difficulties are overcome.

Another object of the invention is to indicate a mechanism of the above kind in which the direction of the forces applied to the edges of the printing plate during the clamping operation easily can be determined by the construction of the mechanism.

A further object of the invention is to indicate a mechanism which provides for a simple intermeshment between the clamping mechanism and the ends of the printing plate when the latter is applied to the plate cylinder.

A still further object is to incorporate adjustment means in the mechanism, which means permit a mutual adjustment in axial direction of the ends of the printing plate during the clamping operation.

Furthermore the mechanism in question should be cheap and reliable in operation.

According to the present invention the bars connected to the ends of the printing plate are adapted to cooperate in such a way with movable members arranged in guides in the walls of the groove that, when the said members are moved towards the bars, cam faces on the said movable members and/ or the said bars cause the latter to be pressed against each other in such a way that the ends of the printing plate are subjected to tensile forces having expedient radial and tangential components. The mutual magnitudes of these components may be adapted to each other within wide limits through the form of the said cam faces in accordance with existing practical conditions.

In order to move the said members towards the bars leftand right-hand threaded pins disposed transversely of the groove may be used meshing with corresponding threaded holes in the movable members. Thus each pin will adjust both bars so that the tightening of the printing plate becomes a very simple operation compared with States Patent the operation of the above mentioned, known mechamsm.

It is expedient that the movable members be so connected to the bars that the latter partake in the movement when the members are moved away from each other, as the pins may also then move the bars away from each other. Thus it is possible to provide for sufficient space to engage the ends of the printing plate with the bars without having to remove the bars from the groove.

Adjusting screws or other adjusting means may be provided at at least one end of the plate cylinder for lengthwise displacement of the bars, which is of importance for obtaining exact registration when adjusting the plate.

Other features of the invention will appear from the following description with reference to the drawings, which depict an embodiment of the mechanism according to the invention.

FIG. 1 shows a plate cylinder of a rotary machine as seen from one end and partly in section along the line II in FIG. 4, a groove being provided at, the circumference of the cylinder for receiving a mechanism according to the invention.

FIG. 2 shows an axial section of the plate cylinder along the line IIII in FIG. 1, taken at the circumference centrally through the groove, a substantial portion of the cylinder being removed at the center of the figure.

FIG. 3 is a top view of the same parts.

FIG. 4 is a section along the line IVIV in FIG. 2, and

FIGS. 5, 6 and 7 show on a larger scale cross sections of the groove along the lines V-V, VI-VI'and VIlVII in FIG. 2, respectively.

As particularly shown in FIG. 1 the plate cylinder 10- at its ends having pivots 12-at its circumference is provided with an axially extending recess 14 of substantially rectangular cross-section.

At the ends of the cylinder this recess is closed by rings 16, FIGS. 2 and 3, which in a known way are attached to turned down faces 18. Extending along the sides of the recess'14- are two rails 20, which by means of screws 24 are attached to a rail 22 which is disposed at the base of the recess 14, FIGS. 2, 5 and 6, the rail 22 then being attached to the cylinder Ml by means of screws 26, FIGS. 2 and 7. At the upper end of their inwardly facing sides the rails 20 have sloping surfaces 28 so that the three rails 20, 20 and 22 together form an undercut groove 30*, the entrance 32 of which disposed at the circumference of the cylinder, is a rather narrow slit. In this groove are disposed two bars 34 which towards the circumference of the-cylinder are wedge formed by mutually inclined surfaces 36, FIGS. 6 and 7, the latter being parallel to the corresponding surfaces 28. To the bars 34 are connected the ends of a flexible plate 38 consisting of a suitable metal, e.g. stainless steel, constituting the printing plate. For attaching the edges 40 of the plate 38 to the bars 34, these latter have in their adjacent side faces narrow axially extending slots 42 which receive the bent edges 40 of the printing plate, which from the circumference of the plate cylinder, where the plate 38 is also bent, extend inwardly to the said slots. Thus a sufficiently effective attachment of the printing plate is achieved, no welding and no removal of the bars from the groove 30 being necessary.

The bars 34- are so shaped, cfr. e.g. FIG. 7, that axially extending, sloping surfaces 44 appear halfway their height.

In the side walls of the groove 30 formed by the rails 20 I rectangular axially extending grooves 46 are provided along each side of the groove 30, each groove 46 forming a guide for a number of elongated blocks 48 which are displaceable in a direction parallel to a plane tangential to the cylinder 10 at the center of the entrance 32 of the groove 30. At their inwardly facing sides the blocks 48 have sloping surfaces 50 which have the same inclination as the surfaces 44 and cooperate with them when the mutually opposed blocks are moved towards each other. By means of this cooperation the bars 34 are pressed towards each other by forces substantially at right angles to the sloping surfaces 44 and 56. The ends of the printing plate 38 which are attached to the bars 34 as described above thus will be subjected to tensile forces which in the shown embodiment have both radial and tangential components. It is easy to see that the magnitudes of these components may be altered by altering the inclination of the sloping surfaces 44 and 54 As shown in FIG. 4 the elongated blocks 48 may be arranged in pairs opposite each other in the grooves 46. In order to move these blocks towards or away from each other there are provided pins 52 being disposed transversely of the groove 30-, said pinsat their ends 54 and 56 left-hand and right-hand threaded, respectivelymeshing with corresponding threaded holes in the blocks 48. Between the bars 34 each pin is provided with a thin disc 58 preferably integral with the pin. As seen in FIG. 2 the discs 58 have notches 60 at their circumference for being turned by means of a hook spanner not shown, which can be introduced through the entrance 32 of the groove. The pins 52 are passed through clearance holes 62 in the bars 34, providing for ample clearance.

As shown in FIG. 4 each pair of blocks 48 is provided with one pin 52 at the center of the blocks. At opposite ends of two opposed blocks 48 screws 64 with heads 66 are screwed into said blocks. The heads 66 are completely or partly received in recesses 68 in the bars 34 which have clearance holes 70 with a diameter slightly larger than the diameter of the screws 64. The latter serve to form a free connection to the bars 34 so as to force the bars to partake in the movement of the blocks 48 when the latter are moved away from each other by turning the screw 52. When the blocks 48 and thus the bars 34 are farthest away from each other, FIG. 5, there will be sufficient space between the bars for engaging the ends of the printing plate with the bars and for removing them from the bars. The printing plate is not shown in FIG. 5.

When the bars 34 are positioned as shown in FIG. 5, it is for practical reasons expedient that they have become exactly fixed in relation to the walls of the groove 30 formed by the rails 20. For this reason the bars 34 are provided with sloping surfaces 72 at their edges which face inwardly against the base of the groove, the said surfaces expediently having the same inclination as the surfaces 36 at their outwardly facing edge, the said surfaces 72 abutting against sloping surfaces 74 on the rails 20. When the bars 34 are moved along with the screws 64 to abut against the sloping surfaces 28 and 74, the bars will occupy exactly defined positions, which facilitates the mounting of the printing plate 38 on the cylinder when the ends of said plate are to engage the bars.

The desired fixing of the bars 34 may be achieved by other means than by the described four sets of complementary sloping surfaces.

When the printing plate 38 is to be tightened on the cylinder 10, the ends of the plate are brought in engagement with the bars 34 as previously described, when the bars occupy the positions shown in FIG. 5. Then the pins 52 are turned by turning the discs 58 in such a direction that the bars 34 are moved towards each other. At the beginning care should be taken that the bent edges 40 still are located in the slots 42. This is shown in FIG. 7. During the following tightening the radial portions of the bent edges will have come so near to the discs 58 that the bent edges 40 now are unable to slip out of the slots 42. The number of pins 52 should be so chosen and the pins should be so evenly distributed over the length of the cylinder that an even tension of the printing plate may be obtained.

When the printing plate is to be removed after use,

the bars 34 are again brought in the position shown in FIG. 5, and the edges of the plate may then be immediately released.

In order to obtain an exact registration when tightening the printing plate, the bars 34 are preferably arranged to be axially slightly displaceable so that a displacement may be performed just before the final tightening of the printing plate over the cylinder. 'It may e.g. be necessary to correct an irregularity caused by the fact that the ends of the plate have not been bent at exactly right angles to the length of the plate, or the printing design may have been arranged slightly askew on the plate. This axial adjustment may be of great practical importance.

In order to achieve this adjustment two screws 76, FIG. 2, are passed through bores in one of the rings 16, the threaded ends of the screws being screwed into angle blocks 78 which are arranged displaceably in corresponding recesses at the end of the groove 30 and are bayonet clutched to the bars 34, as shown in FIG. 2. Each screw has a collar 80, which is received in an annular groove 82 covered by a countersunk disc 84 in the ring 16, said disc being aflixed by means of screws 86. The free ends of the screws 76 are provided with a square neck 88 in order to be operated by means of a suitable key. The collars prevent longitudinal displacement of the screws during the adjustment, so that turning of the screws will cause displacement of the bars 34 in one or the other direction. The said bayonet clutch is arranged in order to prevent the means for axial adjustment becoming a hindrance for the radial and tangential adjustment of the bars 34.

It should be noticed that the clearance holes 62, FIG. 4, should provide for ample clearance, thus allowing the said axial displacement of the bars 34, and the clearance should also allow some movement of the bars in down- Ward direction in the groove 30, when the bars are influenced by the blocks 48. The clearance holes 74} must also allow the said movement of the bars.

In the described embodiment the cam faces mentioned in the introduction of this specification are formed by the sloping surfaces of the bars and the sloping surfaces of the elongated blocks, which latter in the introduction are named the movable members. In order to bring out the desired cam eifect one set of sloping surfaces may suffice, the said surfaces being arranged either on the bars or on the blocks, as the other set may be projections or ribs serving as cam followers during adjustment. The expression cam faces does not necessitate that the surfaces be plane, the shape may e.g. be so that no proportionality is present between the movement of the cam face and the movement of the cam follower. The pins 52 adjusting the bars 34 may be influenced at one of their ends instead of by a disc at their center. In this case e.g. an axially extending shaft may be joumalled in the cylinder at one side of the groove 30, said shaft being in driving connection with the pins by means of conical gear wheels, screw wheels or a worm and a worm wheel, the shaft being influenced at the one end of the cylinder.

Having thus fully described my invention I claim as new and desire to secure by Letters Patent:

1. A mechanism for clamping a flexible printing plate to a plate cylinder having an axially extending groove at its circumference, comprising two bars adapted to be connected to the ends of the printing plate and at their outer edges to support the printing plate, said bars being arranged in said groove in a floating manner with their inner edges abutting each other, guides disposed in opposite side walls of said groove, at least one pair of movable members displaceable in said guides, cooperating cam surfaces arranged on said movable members and said bars between the outer and inner edges of the latter, and means for acting upon said movable members in order to transfer forces via said cam surfaces to said bars, thereby producing movements of the outer edges of the bars, said forces having radial and tangential components depending on the resistance ofiered by the ends of said printing plate.

2. A mechanism according to claim 1, in which the guides for the movable members are directed parallel to a plane tangential to the cylinder at the center of the entrance of the groove.

3. A mechanism according to claim 2, in which the means for acting upon the movable members comprises pins provided with leftand right-hand threads at their opposite ends and arranged transversely of the groove to mesh with corresponding threaded holes in the movable members. 1

4. A mechanism according to claim 3, in which said pins are provided with discs arranged between said bars and adapted to be adjusted by a tool introduced through the entrance of the groove.

5. A mechanism for clamping a flexible printing plate to a plate cylinder having an axially extending groove open at its circumference, comprising two bars positioned freely in the space formed by said groove and connected at their outer edges to the ends of the printing plate whereas their inner edges are adapted to abut against each other, guides disposed in the opposite side walls of said groove, at least one pair of movable members displaceable away from and toward each other in said guides, and sloping cam surfaces provided on said movable members and said bars through which pressure is transmitted from said movable members to said bars to produce movement thereof, said movement having a component directed radially inwardly toward the center of said platecylinder.

6. A mechanism according to claim 5, inwhich the side walls of the groove accommodating the bars are so shaped that the bars are fixed in relation to said cylinder when they are moved away from each other. I

7. A mechanism according to claim 6, n which the bars outwardly towards the entrance of the groove have opposed sloping faces at their outer sides and inwardly towards the bottom of the groove have corresponding opposed sloping faces and that all these sloping faces are adapted to cooperate with sloping faces at the side walls of the groove to keep the bars in fixed position.

8. A mechanism for clamping a flexible printing plate to a plate cylinder having an axially extending groove at its circumference, comprising two bars which are freely arranged in said groove and to which the ends of the printing plate are connected in such a manner that they are supportedby the outer edges of said bars, the inner edges of said bars being adapted to abut against each other, guides disposed at opposite side walls of said groove, at least one pair of movable members slidable in said guides, cooperating cam means provided on said movable members and said bars between the outer and inner edges of the latter, and means operably connected to said movable members for pressing said bars toward each other.

9. A mechanism according to claim 8, in which at least at one end of said cylinder adjusting means are provided for displacing said bars lengthwise in said groove.

10. A mechanism for clamping a flexible printing plate to a plate cylinder having an axially extending groove at its circumference, comprising two bars connected to the ends of the printing plate and being positioned freely in said groove, sloping cam surfaces provided at the outer sides of said bars, and means for applying forces to said cam surfaces in opposite and substantially tangential directions in order to move said bars toward each other and jointly inwardly in the space of said groove.

11. A mechanism according to claim 10, in which each cam surface is shaped as a plane surface inclined in relation to an axial plane through the center of said groove.

12. A mechanism according to claim 8, in which the movable members are arranged in a series at one side of said bars and disposed oppositely to the movable members in the series at the other side of said bars, each pair of opposite members being movable by said last-mentioned means which is a common adjusting means.

13. A mechanism according to claim 8, in which said last-mentioned means consists of a pin with leftand righthand screw threads at its ends, said screw threads intermeshing with corresponding screw threads in said movable members.

14. A mechanism according to claim 13, in which said pin is provided with a disc at its center arranged in the space between said bars.

References Cited in the file ofthis patent UNITED STATES PATENTS 1,582,390 Evans Apr. 27, 1926 1,827,300 Pritchard et a1. Oct. 13, 1931 2,386,214 Harrold et al Oct. 9, 1945 2,745,344 Brodie May 15, 1956 2,775,198 Johnson et al. Dec. 25, 1956 2,820,409 Johnson Jan. 21, 1958 2,837,025 Pechy June 3, 1958 2,910,939 Mosegaard Nov. 3, 1959 FOREIGN PATENTS 698,146 France Nov. 17, 1930 526,837 Great Britain Sept. 26, 1940 

